If you quick-Filter for "new Mails" and kmail is configured to mark new mails (on activation) after 4 Seconds as "readed", the Message disappears out of the list. Here it would be better to keep the message inside of the filterd list, as long as the Message is activatet. See Screencast of the Problem here: http://screencast-o-matic.com/watch/coXv2bh0Bt Reproducible: Always
*** This bug has been marked as a duplicate of bug 259813 ***